Cell culture manufacturing technology is widely used for the production of protein-based products such as pharmaceutical formulations of therapeutic proteins. Commercial production of protein-based products, such as an antibody product, requires optimization of cell culture parameters in order for the cell to produce enough of the protein product to meet manufacturing demands. However, when cell culture parameters are optimized for improving productivity of the protein product it is also necessary to maintain the desired quality attributes of the product such as the glycosylation profile, aggregate levels, charge heterogeneity, and amino acid sequence integrity (Li et al., mAbs, 2010, 2(5):466-477). Another quality attribute of concern is the color of the protein product. Regulatory requirements regarding acceptable color levels for liquid formulations of therapeutic products for human use must be met (United States Pharmacopoeia Inc., 2000, p. 1926-1927 and Council of Europe. European Pharmacopoeia, 2008, 7th Ed. p. 22). Thus, producing a protein product that has an acceptable color is an important aspect of therapeutic protein production.
Recent trends towards the subcutaneous delivery of therapeutic proteins, such as monoclonal antibodies, has been accompanied by an increase in concentration of the formulated protein substance, for example at concentrations about 100 mg/mL or greater (Daugherty et al., Adv Drug Deliver Rev, 2006, 58(5-6):686-706). A correlation between increased color intensity in compositions comprising increasing amounts of therapeutic protein has been observed and this relationship may be due low-level protein product variants previously unobservable by standard methods for monitoring color intensity of the formulated product.
Oxidation is a major chemical degradation pathway for protein pharmaceuticals. For example, methionine, cysteine, histidine, tryptophan, and tyrosine are amino acid residues that are susceptible to oxidation due to their reactivity with reactive oxygen species (ROS) and this oxidation is often observed in pharmaceutical protein formulations during storage. Although it is known that cell culture conditions can impact quality attributes of the protein product, such as production of sufficient amounts for large-scale manufacturing, the impact of these conditions on the color intensity of the final protein product remains unclear.
There is a continuing need to provide improved and cost-effective methods of producing proteins (e.g., antibodies) having acceptable product quality attributes such as color intensity. Cell culture media, whether chemically undefined or chemically defined, having components that consistently deliver protein products at lower color intensities while maintaining a desired protein concentration (e.g., ≥100 mg/mL) would find use in the development of protein products, such as antibodies.